I've used the trial version of LR CC on my Macbook Pro at home for several weeks, just bought a CC membership. Works fine on my laptop.

Just downloaded LR to desktop PC at work, everything functions as normal EXCEPT that when I select imported photos in filmstrip, the loading task bar will begin, but once completed there is nothing but a grey background in the viewer canvas.

Photos ARE visible in the Library module, but disappear once I select develop module.